This present invention relates to manufacture of electrochemical cells. More particularly, the present invention provides a method and a system for operating a battery in a selected application. Merely by way of example, the invention has been provided with use of lithium based battery cells, but it would be recognized that other battery cells made from materials such as zinc, silver and lead, nickel could be operated in the same or like fashion. Additionally, such batteries can be used for a variety of applications such as portable electronics (cell phones, personal digital assistants, music players, video cameras, and the like), tablet and laptop computers, power tools, power supplies for military use (communications, lighting, imaging and the like), power supplies for aerospace applications (power for satellites and micro air vehicles), and power supplies for vehicle applications (hybrid electric vehicles, plug-in hybrid electric vehicles, and fully electric vehicles). The method and system for operation of such batteries are also applicable to cases in which the battery is not the only power supply in the system, and additional power is provided by a fuel cell, other batteries, an IC engine or other combustion devices, capacitors, solar cells, etc.
In the context of batteries, it is desired in some applications to be able to estimate quantities that are descriptive of the present battery condition, but that may not be directly measured. Some of these quantities may change rapidly, such as the sate of charge, which can traverse its entire range within minutes. In the context of the battery systems, particularly those that need to operate for long period of time, as aggressively as possible without harming the battery life, for example, in hybrid electric vehicle batteries, laptop computer batteries, portable tool batteries, and the like, it is desired that information regarding state of charge is accurate and fast so one can further control the power/energy output of the batteries, determine if it is necessary to charge the batteries, and determine the health of batteries.
As an example, the use of estimation of parameters for a battery cell has been described in U.S. Pat. No. 7,315,789, in the name of Gregory L. Plett and assigned to LG Chemical Ltd., which is incorporated by reference herein. Plett disclosed the use of a Kalman filter and/or extended Kalman filter. Limitations, however, exists. Although somewhat successful, Plett's techniques are not robust and yield poor performance since they fail to converge for highly nonlinear cases, are cumbersome, and difficult to apply in complex electrochemical systems. These and other limitations are overcome by the present method and system as further described throughout the present specification below.